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International Academy of Gnathology

---American Section---

September 1985

The International Academy of Gnathology is pleased to present this second edition of the Glossary of Occlusal Terms. We hope it will prove useful, particularly to lecturers and scientific writers. We wish to commend Dr. William McHorris and his committee for the excellent fulfillment of their assigned project.

Dr. Charles G. Eller,President

Formulated by the Glossary Committee of the International Academy of Gnathology

It is not the intent of this glossary to take the place of more definitive works in the dental field. This glossary is an attempt to help eliminate the confusion facing teachers and writers of scientific information by providing the terminology that would make communication consistent and uniform.

PREFACE

Gnathology and maxillofacial prosthetics have used a number of terms not commonly employed by other disciplines in dentistry. Dr. Harvey Stallard saw the need for proper communication with a common glossary of terms. Definitions of some terms have to be uniquely related to the philosophies and techniques of particular professions, otherwise the original purpose of technical terminology is lost.

The terms in this glossary are alphabetically arranged, and the most grammatically correct term was used to help clarify the confusion presented by similar terms used frequently in the past.

It is the purpose of this glossary to provide the most succinct possible definition of terms, and only those definitions that have a direct gnathologic context.

I wish to gratefully acknowledge the assistance of the committee, and it is our hope that this second edition will be a meaningful step forward in the field of gnathology so that each of us may have a more consistent basis of communication.

Advancement, mandibular or maxillary - The anterior positioning of the mandible or maxillae during certain orthognathic surgical procedures (Also see surgery, orthognathic).

Analysis - Separation into component parts for the purpose of correlation.

Bite A. - (See analysis, functional occlusal).

Cephalometric A. - Evaluation of the growth pattern or morphology of the head based on tracing of a cephalogram.

Functional Occlusal Analysis - Evaluation of the occlusal surfaces of the teeth as they relate to each other in static and moving positions. Generally accomplished on casts anatomically mounted in an articulator.

Angle - Degree of divergence of two intersecting lines or planes.

Arrow Point A. - The angle associated with the functional fossae of maxillary posterior teeth which is formed by the coalescing of the shearing and stamp ridges and related grooves. Those angles are indicative of the dynamic pathways of the stamp cusps in working and non-working movements. The apices of these angles are directed posteriorly.

Bennett A.- Commonly recognized and accepted as the angle formed between the protrusive and nonworking lines of the pantogram on the posterior horizontal recording plate.

Condylo-incisal A. (Condylar incisal A.) - The angle formed by the intersection of the radial line which extends from the horizontal condylar axis and the line representing the long axis of the mandibular central incisor.

Disclusive A. - The angle formed by the intersection of the axis-orbital plane (horizontal) and a line representing the path of mandibular movement in any eccentric excursion viewed in the sagittal or frontal planes. (See also disclusion).

Anterior Disclusive A. - The angle formed by the intersection of the axis-orbital plane (horizontal) and the line representing the disclusive pathway provided by the anterior teeth. This angle should be similar to and dictated by the condylar disclusive angle.

Condylar Disclusive A. - The angle formed by the intersection of the axis-orbital plane (horizontal) and the line representing the disclusive pathway provided by the condyles.

Fischer A. - The angle formed by the protrusive and non-working condylar paths,viewed in the sagittal plane.

Frankfort-mandibular incisor A. (FMIA) - Angle formed by the intersection of a line representing the long axis of the mandibular central incisor and the Frankfort horizontal plane.

Gothic Arch A. -The angle associated with the functional fossae of mandibular posterior teeth which is formed by the coalescing of the shearing and stamp ridges and related grooves. Those angles are indicative of the dynamic pathways of the stamp cusps in working and non-working movements. The apices of these angles are directed anteriorly.

Anterior nasal spine (ANS) - Cephalometric landmark; tip of the anterior nasal spine as seen on a cephalogram from a lateral view.

Appliance - A device used to provide function or therapeutic effect during the treatment phase. Definitive restorations such as complete, removable partial, or fixed partial dentures, obturators, crowns, etc., are not classified as appliances. (See also orthosis, oral).

Functional Jaw Orthopedic A. - A removable device used to effect changes in jaw position and tooth alignment based on the principle of using muscle function. (See also orthosis, oral).

Gnathologic Orthopedic A. - Any number of removable appliances (Crozat, Kernot, Bionator, Bimler, etc.) used to encourage and guide the growth of the bony structure itself so that there will be sufficient space for all the teeth in their appropriate positions resulting in beneficial arch development. (See also orthosis, oral).

Occlusal A. - (bite plane, bite guard, night appliance) An appliance, usually of resin or metal, fabricated to cover the occlusal and/or incisal surfaces of the maxillary or mandibular teeth (and sometimes both), for the purpose of diminishing the traumas of bruxing and clenching habits to the teeth, periodontium, the temporomandibular joints, and the muscles of the mastication. (See also orthosis, oral).

Occlusal Orthopedic A. - An occlusal appliance used as an adjunct for diagnosis of occlusal problems. It allows a reversible means of eliminating interceptive occlusal contacts thereby deprogramming the proprioceptive engrams from the teeth to the muscles and joints. It enables the development of an organized pattern of occlusal contacts with an appropriate anterior disclusive angle providing for separation of posterior contacts in any movement away from the initial position. Once the appliance is inserted, subsequent adjustments are usually necessary in order to accommodate changing mandibular position relative to the maxillae and to ascertain resolution and a stable centric relation position. (See also orthosis, oral).

Orthodontic A. - A device (fixed, removable, or combination thereof) designed to move teeth into a more esthetic and functional (physiologic) alignment within the dental arch and in relationship to the opposing dentition. (See also orthosis, oral).

Dental A. - The orientation of the maxillary and mandibular teeth in static and dynamic relationships.

Temporomandibular A. - (See joint, temporomandibular).

Articulator - A mechanical device which represents the temporomandibular joints and has upper and lower members to which dental casts may be attached.

Highly Adjustable A. - An articulator that can be programmed to receive and simulate mandibular movement capabilities to a high degree of accuracy.

Non-adjustable A. - An articulator that is limited to opening and closing movements.

Semi-adjustable A. - An articulator that can be programmed to receive and simulate some mandibular movement capabilities; usually limited to straight line excursions or movements.

Attrition - (See abrasion).

Axes of Rotation - The three basic imaginary axes of the mandibular condyles about which mandibular movement occurs. The three axes are the vertical (superior-inferior), the sagittal (anterior-posterior), and the horizontal (medial-lateral). The horizontal axis is referred to as the hinge or transverse mandibular axis. Each axis of rotation is perpendicular to the other two and is constant to the condyles regardless of their anatomic position.

Axial force - (See force, axial).

Axis - An imaginary straight line about which a body may rotate.

Condylar A. - (See axis, transverse mandibular).

Hinge A. - (See axis, transverse mandibular).

Horizontal A. - (See axis, transverse mandibular).

Opening A. - (See axis, transverse mandibular).

Sagittal Axis. - An imaginary line extending anteroposteriorly through the working condyle about which the mandible rotates during a working movement. If it were visible, it would appear as a point in the frontal plane.

Terminal Hinge A. - The transverse horizontal axis of the mandibular condyles when the condyles are in centric relation. This axis may be located and marked as the posterior reference points.

Transverse Mandibular A. - The transverse horizontal axis of the mandibular condyles round which the mandible rotates during opening and closing movements. It is locatable and can be viewed in the sagittal plane.

Vertical Axis - An imaginary line extending through the working condyle in a superiorinferior direction about which the mandible rotates during a working movement. If it were visible, it would appear as a point in the horizontal plane.

Axis-Orbital Plane - (See plane, axis-orbital).

Axis Point - (See point, hinge axis).

Axis Point, Arbitrary - (See point, axis, arbitrary).

Axis Transfer - The act of transferring the located transverse mandibular axis of the patient to the axis of the articulator by means of a facebow. (See also facebow; record, facebow).

B

B Point - (See point, B).

Balanced - (See occlusion, bilaterally balanced).

Balancing Contact(s) - (See contact(s), non-working).

Balancing Side - (See side, non-working).

Baison (Ba) - The midline point at the anterior margin of the occipital foramen.

Bennett Angle - (See angle, Bennett).

Bennett Movement - (See movement, Bennett).

Biomechanics - 1. The Science which deals with the forces that act on living cells of the body. 2. The relationship between the biologic behavior of living structures and the physical influence to which these structures are subjected.

Bite - The word -bite- used alone should be reserved for the act of incision of a morsel of food and in connection with discussion of the amount of pressure developed in closing the jaws, etc.

Bruxism - An involuntary, parafunctional, excessive clenching, rubbing, or grinding of the teeth usually performed during sleep; often triggered by anxiety, emotional stress or fatigue, and frequently associated with occlusal irregularities. The frequency and duration of bruxing episodes may be enhanced by habitual sleeping postures.

C

Canine-protected occlusion - (See occlusion, mutually protected).

Capsule, temporomandibular joint - The fibrous sac which encloses the temporomandibular joint. It is lined with a synovial membrane and filled with synovial fluid.

Adaptive arcs of C. (adjustive arcs of C., voluntary arcs of C.) - Arcs of mandibular closure found in mouths with deflective occlusal contacts resulting in maximum intercuspation of the teeth that do not coincide with a centrically related closure of the mandible.

Skeletal arcs of C. (centric relation arcs of C.) - Arcs of mandibular closure found when the condyles are centrically related.

Clutch - A custom-fitted or fabricated device for the maxillary and mandibular components for the purpose of supporting extraoral recorders, hingebows, facebows, etc.

Compensating Curve - (See curve of Spee).

Condylar axis - (See axis, transverse mandibular).

Condylar guidance - (See disclusion, condylar).

Condylar inclination - (See inclination, condylar).

Condyle - The rounded surface at the articular end of a bone.

Mandibular C. - The articular process of the mandible.

Non-working C. (orbiting C., balancing C., idling C.) - The condyle opposite the working condyle; is assumes an orbiting pathway or movement about the rotations of the working condyle. When the working side is moving laterally, the non-working pathways of movement would be medially downward, and forward.

Working C. (rotating C.) - The condyle on the same side of the dentition on which the chewing occurs and toward which the mandible has been moved. During lateral functional movements, this condyle serves as the center of rotation for the mandible.

-A- O.C. - Denotes those contacts which occur when the shearing cusp components of the maxillary teeth occlude with the stamp cusp components of the mandibular teeth.

-B- O.C. - Denotes those contacts which occur when the stamp cusp components of the maxillary teeth occlude with the stamp cusp components of the mandibular teeth.

-C- O.C. - Denotes those contacts which occur when the stamp cusp components of the maxillary teeth occlude with the shearing cusp components of the mandibular teeth.

Closure stopper O.C. - Those contacts occurring on the mesial inclines or slopes of mandibular teeth and on the distal inclines of maxillary teeth. These contacts stop the closure of the mandible.

Equalizer O.C. - Those contacts occurring on the distal slopes or inclines of mandibular teeth and on the mesial incline of maxillary teeth. These contacts equalize the forces placed on the teeth by closure stopper occlusal contacts.

Protrusive C. - Any contact which occurs on the parts of opposing teeth in protrusive excursions.

Working C. - Contacts between opposing teeth on the working (chewing) side during mandibular movement.

Coronal plane - (See plane, frontal).

Costen-s syndrome - (See syndrome, Costen-s).

Coupling - The static, together, closed relation of opposing parts. A term used to designate the approximation of the maxillary and mandibular anterior teeth when the posterior teeth are at maximum intercuspation.

Curve - Non-angular deviation from a straight line.

C. of Spee - A curve described by -Von Spee,- viewed in the sagittal plane, formed by a line from the tip of the canine, the facial cusp tips of premolars and molars, and continuing to the anterior border of the ramus.

C. of Wilson - A curve, described by Wilson, viewed in the frontal plane by facial and lingual cusp tips. This curvature is caused by the inclination of the long axes of the mandibular teeth toward the lingual and of the maxillary teeth toward the facial.

Cusp(s) - Any crown elevation which begins calcification as an independent center. A notably pointed or rounded eminence on or near the masticating surface of a tooth.

C. height - The vertical distance between two parallel planes passing at right angles to the long axis of the tooth through the crown so that on plane contains the highest point of the cusp and the other contains the lowest point of the fossa.

Shearing C. - Those cusps which pass closely by opposing stamp cusps in working (chewing) excursions for the purpose of shearing or cutting food. In normal relations, this would include the facial cusps of maxillary posterior teeth, the lingual cusps of mandibular posterior teeth, and the lingual contours of all maxillary teeth.

Stamp C. - Those cusps which seat into an opposing fossa or embrasure; centric holding cusp; in normal relations, this would include the lingual cusps of the maxillary posterior teeth, the facial cusps of the mandibular posterior teeth, and the cusps of all mandibular anterior teeth.

Vertical D. - A vertical measurement of the face between any two arbitrarily selected points that are conveniently located one above and one below the mouth, usually in the midline.

Decreased Vertical D. - Decrease the vertical distance between the mandible and the maxilla.

Increased Vertical D. - Increase the vertical distance between the mandible and the maxilla.

Occlusal Vertical D. - The vertical dimension or height of the face when the teeth are at maximum intercuspation.

Rest Vertical D. - The vertical dimension or height of the face with the mandible in the rest position.

Disc, Temporomandibular articular - An oval plate of fibrous tissues that is attached circumferentially within the temporomandibular joint capsule and divides the joint into a superior and inferior compartment. It is a concavo-convex structure with a center area thinner than its thicker peripheral borders. The center area is the bearing surface between the articular eminence and the articular process of the condyle which allows the superior and inferior surfaces to function as true articular facets. The articular disc functions as a -non-ossified bone- which enables the temporomandibular joint to be classified as a compound joint. (See also joint, temporomandibular).

Disclusion - The act of separating the contacting surfaces of opposing teeth; the opposite of occlusion. Physiologic disclusion is ordinary separation of the teeth during functional movements. In bruxing attempts, the acts of disclusion can be achieved by the condyles and the mandibular anterior teeth.

Anterior D. - Occasioned by the descent of the mandibular anterior teeth against the lingual surface of the opposing maxillary teeth resulting in sufficient downward movement to separate the posterior teeth.

Condylar D. - Occasioned by the descent of the condyle-disc assemblies as they engage the articular eminence resulting in sufficient downward movement of the mandible to separate the posterior teeth.

Distance - The measure of space intervening between two points of reference.

Intercondylar D. - The distance between the rotational centers of the mandibular condyles.

Interocclusal D. - The vertical distance between the maxillary and mandibular teeth when the mandible is in its physiologic rest position. This can be determined be calculating the difference between the rest vertical dimension and the occlusal vertical dimension of the face. (See also space, freeway).

Eminence - A prominence or projection, especially one upon the surface of a bone; also called eminentia.

Articular eminence (temporomandibular articular E.) - The articular surface of the glenoid fossa of the temporal bone. The slope of the articular eminence is significant in that it dictates the path of movement of the condyles in eccentric excursions.

Envelope of function - (See function, envelope of)

Envelope of motion - (See motion, envelope of)

Equilibration - The act of placing a body or object in a state of equilibrium.

Diagnostic E. - The act of recontouring by selective cutting on mounted dental casts to determine and evaluate the deflective contacts on teeth to ascertain what corrections would be needed to achieve the desired result in the mouth.

Facebow - A caliper-like device used to record the relationship of the maxilla to the transverse mandibular axis of the mandibular condyles and to the axis-orbital plane. It will orient the maxillary cast in this same relationship to the transverse mandibular axis and the upper member of an articulator. (See also Record, Facebow).

Adjustable axis F.B. - (Axis transfer bow) (See facebow, kinematic).

Kinematic F.B. - A facebow whose caliper ends can be adjusted to accept the accurate location of the axis of rotation of the mandible.

Facet, wear - A flattened, high glazed wear pattern visible on teeth.

Fluid, synovial - The small amount of fluid occurring in joints. It contains approximately 95% water with only 1-2% protein. Its function is to lubricate joint surfaces and nourish the articular connective tissue.

Force - An influence that changes or tends to change motion in a body.

Anterior component of F. - The force distributed to teeth in an anterior direction as a result of the mechanics induced by the hinge-type closure of the mandible, usually resulting in an anterior drift of all the teeth.

Axial F. - The force exerted in line with the long axis of a tooth.

Masticatory F. - The force applied by the muscles of mastication during the act of chewing.

Occlusal F. - Any force applied to the occlusal surfaces of teeth.

Fork, facebow - That part of the facebow assembly used to record the maxillary components and to facilitate proper transfer of the maxillary cast to the articulator.

Fossa - A pit, hollow or depression.

F. depth - The vertical distance between two parallel planes passing at right angles to the long axis of the tooth through the crown so that one plane contains the highest point of the shortest cusp and the other contains the lowest point of the fossa.

Glenoid F. (mandibular F.) - The fossa of the temporal bone into which the condyles of the mandible articulate.

Envelope of F. - That portion of the envelope of motion restricted to the contact relationships of teeth.

Group F. - The simultaneous contact of opposing teeth in a segment or group; generally a term used to identify the sharing of force on contacting surfaces of the teeth on the working side only; unilateral balanced occlusion.

Physiological F. - The degree of activity that stimulates the physical structures but which stops short of irritation of those tissues; function that does not exceed the tissues- ability to resist.

Gnathology - The science that studies and treats the biologics of the masticatory mechanism; that is, the morphology, anatomy, histology, physiology, pathology and the therapeutics of the oral organ, especially the jaws and the teeth and the vital relations of this organ to the rest of the body.

Gonion (Go) - Cephalometric landmark; the lowest, posterior and most outward point of the mandibular angle.

Gothic arch tracing - (See tracing, needle point).

Groove - A linear channel or sulcus.

Developmental G. - Finely depressed lines in the enamel of a tooth in its development. They have sharp bottoms and extend to and through the marginal ridges of teeth. They are the suture lines between the major lobes of teeth.

Supplemental G. - A groove which is a tributary of a developmental groove, shallow in nature with a rounded bottom, but does not usually extend through the marginal ridge of the occlusal surface of a tooth.

Group function - (See function, group).

Guard, bite (guard, mouth; guard, night) - (See splint, occlusal).

Guidance - A mechanical or other means of controlling the direction of movement of an object.

Anterior G. (incisal G.) - (See disclusion, anterior).

Condylar G. - (See disclusion, condylar).

H

Hinge axis - (See axis, transverse mandibular).

Hingebow - (See facebow).

Horizontal overlap - (See overlap, horizontal).

Horizontal plane - (See plane, axis-orbital).

Horizontal axis - (See axis, transverse mandibular).

I

Immediate side-shift - (See side-shift, immediate).

Incisal angle - (See angle disclusive, anterior).

Incisal guidance - (See disclusion, anterior).

Incisal guide table - (See table, stop guide).

Inclination - The angle of slope from a particular plane of reference.

Condylar I. - The angle of the pathway of descent taken by the condyle when the mandible moves to later protrusive or lateroprotrusive positions, the mechanical angle set into articulators from stylus tracings or eccentric interocclusal records to reproduce the slope of the articular eminence.

Intercondylar distance - (See distance, intercondylar).

Intercuspation, maximum (acquired occlusion, centric occlusion, habitual occlusion) - The most closed , static position which the mandible assumes determined by the full interdigitation of opposing teeth, irrespective of condyle centricity. (See also occlusion, maximum intercuspation).

Interference, occlusal - (See contact, deflective).

Interocclusal distance - (See distance, interocclusal).

Interocclusal record - (See record, interocclusal).

J

Jaw - The common name for either the maxilla or mandible.

J. joint - (See joint, temporomandibular).

J. relation - (See relation, jaw).

Joint - The junctions between bones and cartilages.

Ginglymus J. (hinge joint) - A joint that allows motion around an axis.

Hinge J. - (See joint, ginglymus).

Mandibular J. - (See joint, temporomandibular).

Temporomandibular J. (Mandibular joint, temporomandibular articulation) - The articulation between the mandible and the cranium. The joint is composed of the mandibular condyle and the glenoid fossa of the temporal bone. An articular disc is interposed between these two osseous members resulting in an upper and lower compartment within the joint capsule. Translation of the mandible occurs in the upper chamber, while only hinge movement occurs in the lower. The joint is paired, right and left, and each may act as an axis of rotation for the other during lateral movements. Each may limit the range of motion of the other.

K

Kinematic facebow - (See facebow, kinematic).

Kinesiology - The study of human motion that attempts to explain the manner in which movements of the body occur by considering collectively the information from the areas of anatomy, physiology and mechanics.

L

Laminagraphy - Body section radiography; radiography at predetermined or desired levels of depth, used in dentistry in temporomandibular joint projections.

Lateral - A position either to the right or left of the mid-sagittal plane; to either side of the midline.

L. checkbite - (See record, interocclusal, eccentric, lateral).

L. excursion - (See movement, excursive).

L. interference - (See contact, deflective).

L. movement - (See movement, dynamics of mandibular).

Laterodetrusion - (See movement, dynamics of mandibular).

Lateroprotrusion - (See movement, dynamics of mandibular).

Lateroretrusion - (See movement, dynamics of mandibular).

Laterotrusion - (See movement, dynamics of mandibular).

Lever - A bar or rigid body that is capable of rotating about one point or axis and in which are two or more other points where forces are applied. There are three classes of levers, and each has its own most effective use.

Class 1 L. - A lever in which the fulcrum lies between the power source and the work produced. The most efficient lever system.

Class 2 L. - A lever in which the fulcrum is at one end, the effort or power at the other, and the load in between. Thus, the force arm is always longer than the work-producing arm, and the work produced is always greater than the energy used, with a resultant high efficiency.

Class 3 L. - A lever in which the axis is at one end, the load at the other, and the effort or power is exerted at a point in between. This is the least efficient of the levers.

Line - Boundary, demarcation.

Camper-s L. - The line running from the inferior border of the ala of the nose to the superior border of the tragus of the ear.

Fulcrum L. - An imaginary line around which a removable partial denture tends to rotate.

Non-working L. (orbiting L., idling L.) - The tracing on a mandibular movement recorder that starts from the point of centricity and on the posterior horizontal recording plates runs forward and medially, but on the posterior vertical recording plates runs forward and downward, when the styli are attached to the mandible.

Protrusive L. - One of the three tracings made on each of six recording plates of a mandibular movement recorder. If the recording plate is attached to the mandible, the stylus will scribe a backward line from the point of centricity. If the recording plate is attached to the maxillae the line scribed by the stylus will be forward from the point of centricity.

Working L. - The tracing on a mandibular movement recorder that starts form the point of centricity and runs laterally on the horizontal plates and posteriorly on the vertical plates, when the styli are attached to the mandible.

M

Malocclusion - Improper occlusion of the lower teeth with the upper teeth.

Deflective M. - A type of malocclusion which is not in agreement with the physiological centricity of the condyles; the deflectors on the occlusal surfaces force the condyles to assume compensating acquired eccentric positions.

Mastication - The process of chewing food in preparation for swallowing and digestion.

Forces of M. - (See force, masticatory).

Maxilla - Upper jaw.

Maxillary - Pertaining to the maxilla.

M. advancement - (See advancement, maxillary).

Maxillomandibular relation - (See relation, jaw).

Maximum intercuspation - (See intercuspation, maximum).

Median sagittal plane - (See plane, sagittal).

Mediotrusion - (See movement, dynamics of mandibular).

Meniscus - (Objectionable term; See disc, articular). Note: Considerable misunderstanding has resulted from the inaccurate use of this term. An anatomical meniscus (Greek meniskos, crescent) is a crescent-shaped fibrocartilagenous structure having one edge attached to the articular capsule and the other extending freely into the joint cavity. Thus, a true meniscus does not separate the joint cavity, nor isolate the synovial fluid, but it functions passively to facilitate movement between the bony parts. Typical meniscuses are those of the knee joint where hinge action is the principle movement. Therefore the articular disc of the temporomandibular joint is not a meniscus at all.

Morphology - The science that deals with the form and structure of an organism or part.

Occlusal M. - The configurations of the elevations and depressions of the occlusal surfaces of the teeth; occlusal anatomy.

Determinants of O.M. - The anatomical factors (angle of eminence, side shift, etc.) which dictate mandibular movement and have an effect on the morphology of teeth, e.g., ridge and groove direction, cusp height, fossa depth.

Motion, envelope of - The three-dimensional space circumscribed by border movements and by occlusal contacts of a given point of the mandible.

Movement - Any change of place, position or posture of a body.

Bennett M. (transtrusion, side shift) - The bodily side thrust or shift of the mandible regulated by the anatomical configurations of the glenoid fossa or the capsular ligaments. (See also movement, dynamics of mandibular).

Border M. - The circumferential limit of mandibular movement capabilities; the forward, backward and lateral extremes of the condyles.

Determinants of mandibular M. - Any anatomical structure or structures which dictate the movement of the mandible, usually limited by the ligaments and bone of the glenoid fossa and accomplished by the muscles of mastication.

Dynamics of mandibular M. - The bodily movements of the mandible about the three axes of rotation in the three planes of space, the result being three- dimensional movement incorporating the fourth dimension of time.

Terms affixed to these movements are as follows:

Detrusion - Downward thrust.

Protrusion - Forward thrust.

Retrusion - Backward thrust.

Surtrusion - Upward thrust.

Transtrusion - The bodily side shift of the mandible; across thrust (Bennett movement).

1.Medio-trusion - Side thrust medially or inward; a capability of a condyle in non-working movements resulting in a medial downward and forward thrust of the non-working condyle.

2.Latero-trusion - Side thrust laterally or outward; a capability of a condyle in working movements. Other terms affixed to the capabilities of the working condyle are:

a. Latero-detrusion - Outward and downward thrust.

b. Latero-protrusion - Outward and forward thrust.

c. Latero-pro-detrusion - Outward, forward and downward thrust.

d. Latero-pro-surtrusion - Outward, forward and upward thrust.

e. Latero-retrusion - Outward, and backward thrust.

f. Latero-re-detrusion - Outward, backward and downward thrust.

g. Latero-re-surtrusion - Outward, backward and upward thrust.

h. Latero-surtrusion - Outward and upward thrust.

Excursive M. - Any movement of the mandible away from centric relation.

Occlusion - The static, closed position of lower teeth to upper teeth. (See also intercuspation, maximum).

Acentric O. - (See occlusion, eccentric).

Anterior determinants of cusp O. - The characteristics of the anterior teeth which determine the cusp height and fossa depth of the posterior teeth; their positions, their inclinations, their horizontal and vertical overlaps, their anatomy, and their ability to disclude in harmony with the condyles.

Bilaterally balanced O. - An occlusion in which both sides of the dental arch are in contact with their opponents during tooth contacting excursions of the mandible.

Unilateral balanced O. - An occlusion in which only the teeth on the working side of the dental arch contact their opponents during mandibular movement; group function.

Centric O. - (See occlusion, maximum intercuspation).

Centric relation O. - The occlusion noted when the teeth are in maximum intercuspation and the condyles are centrically related in the glenoid fossa. Any other occluded position would have to be considered eccentric occlusion. (See also relation, centric).

Cusp-embrasure O. - An occlusal arrangement in which each tooth has two opponents; tooth-to-two-tooth occlusion.

Cusp-fossa O. - An occlusal arrangement in which each tooth has only one opponent; tooth-to-tooth occlusion.

Eccentric O. - Any occlusion other than centric relation occlusion.

Edge-to-edge O. (end-to-end O.) - An occlusion in which the anterior teeth of both jaws meet along their incisal edges when the teeth are in maximum intercuspation.

Functional O. - Occlusion in which attention is directed specifically to performance and is differentiated from structure and appearance.

Maximum intercuspation O. (acquired occlusion, centric occlusion, habitual occlusion) - The full interdigitation of opposing teeth irrespective of condyle centricity. If this interdigitation occurs with the condyles in centric relation, this would be defined as centric relation occlusion.

Mutually protected O. - An occlusion in which the posterior teeth protect the anterior teeth in centric relation closure and the anterior teeth protect the posterior teeth in any movement or position away from the centric relation position. In bruxing attempts, this allows the anterior teeth to prevent lateral, protrusive or other moving forces to the posterior teeth.

Pathologic O. - An occlusion which is not in sufficient harmony with the anatomic and physiologic controls of the mandible to prevent pathological changes in the tissues of the gnathic system. (See also occlusion, traumatic).

Physiological O. - An occlusion which is in sufficient harmony with the anatomic and physiologic controls of the mandible so that pathology is not precipitated.

Plane of O. - (See plane, occlusal).

Traumatic O. - An occlusion which results in injury to the teeth or supporting structures. (See also occlusion, pathological).

Open bite - (See bite, open).

Orbitale (Or) - Cephalometric landmark; the lowest point in the margin of the orbit.

Orbiting condyle - (See condyle, non-working).

Orbiting path - (See path, non-working).

Orthognathic surgery - (See surgery, orthognathic).

Orthopedic - Pertaining to the correction of skeletal deformities; concerned with the preservation and restoration of the function of the skeletal system, its articulations and associated structures.

Orthosis - An orthopedic appliance or apparatus used to support, align, prevent or correct deformities or to improve the function of movable parts of the body.

Orthosis, oral - Pertaining to an orthosis for the gnathic system.

Orthotic - Serving to protect or to restore or improve function; pertaining to the use or application of an orthosis.

Overbite - (See overlap, vertical).

Overjet - (See overlap, horizontal).

Overlap - To lie or extend over and cover part of.

Horizontal O. (overjet) - Projection of the anterior and/or posterior teeth of one arch beyond their antagonists in a horizontal direction when the opposing posterior teeth are occluded.

Vertical O. (overbite) - Projection of the upper teeth over the lower teeth in a vertical direction when the opposing posterior teeth are occluded.

Deep V.O. - Excessive vertical overlap of the anterior teeth.

P

Palpate - To examine by the hand; to feel.

Pantogram - The record of a recording instrument (Pantograph) in the form of traced lines.

Pantograph - An instrument for copying. An instrument, fixed to the maxilla and mandible, capable of recording the movements of the mandible. Such records may then be used to program and instrument capable of simulating the movements of the mandible.

Path - A certain course that is ordinarily followed.

P. of closure - The path traversed by the mandible during closure when it-s associated neuromuscular mechanism is in a balanced state of tonus and the condyles are centrically related.

Condyle P. - The paths followed by the mandibular condyles during all movements of the mandible. (See also inclination, condylar; angle, condylar, disclusive).

Non-working P. (orbiting P., idling P., balancing P.) - Path followed by the non-working condyle or the stamp cusps of the teeth on the non-working side during mandibular movements.

Generated occlusal P. - The paths of movement of the occlusal surfaces of teeth registered on a wax, plastic, or abrasive surface attached to the opposing dental arch.

Working P. - The path followed by the working condyle or the cusps of the teeth on the working side during mandibular movement.

Periauricular - The area surrounding the external ear.

Preauricular - The area anterior to the external ear.

Physiological occlusion - (See occlusion, physiological).

Pin - A small cylindrical piece of metal.

Incisal Stop P. - A metal rod which is attached to the upper member of an articulator and contacts the stop table. It can be used to maintain an established dimension between the members of the articulator.

Plane - An ideal flat surface.

Axis-orbital P. - The horizontal plane that passes from the hinge axis of the condyles through the inferior border of the bony orbit (orbitale).

Bite-P. - (See appliance, occlusal; occlusal orthopedic).

Camper-s P. - A plane extending from the inferior border of the ala of the nose to the superior border of the tragus of the ear.

Frankfort horizontal P. - The eye-ear plane. A plane passing through the lowest point in the margin of the orbit (orbitale) and the highest point in the margin of the auditory meatus (tragion).

Frontal P. (coronal plane) -The vertical mediolateral median plane of the body, dividing the body into front and back portions.

Occlusal P. - An imaginary surface that is related anatomically to the cranium and that theoretically touches the incisal edges of the incisors and the cusp tips of the occluding surfaces of the posterior teeth. It is not a plane in the true sense of the word, but represents the mean of the curvature of the surface.

Sagittal P. - Any vertical plane that passes through the body parallel to the median plane and divides the body into left and right portions.

Plates, reference - An adjustable device that can be fitted to the maxillary and mandibular components utilizing a central bearing device for the purpose of supporting extraoral recorders, hingebows, facebows, etc.

Pogonion (Pog) - Cephalometric landmark; the most anterior prominent point on the chin.

Point A - Cephalometric landmark (subspinale); deepest midline point on the premaxilla.

Point B - Cephalometric landmark (supramentale); most posterior point in the concavity between infradentale and pogonion.

Hinge axis P. - A point placed on the skin corresponding with the transverse mandibular axis of the mandible. (This point should be marked when the mandible is in the centric relation position; terminal hinge position).

Third reference P. - A point of reference usually on the axis-orbital plane that enables proper mounting of maxillary casts in facebow transfer procedures. This point can be permanently marked on the skin, usually on the side of the nose.